What is correct concerning TI (Therapeutic Index)?

Correct Answer: A

Rationale: The correct answer is A because the therapeutic index (TI) is a measure of a drug's safety margin. A higher TI indicates a safer drug as it represents the ratio between the dose that produces therapeutic effects and the dose that causes toxicity. If the therapeutic dose is much lower than the toxic dose, it results in a higher TI, indicating a safer drug. Choice B is incorrect because a TI of 1 indicates that the therapeutic dose is equal to the toxic dose, which is not desirable. Choice C is incorrect as the presence of unwanted adverse effects does not necessarily impact the TI directly. Choice D is incorrect because the margin of safety for Digoxin is 0.8-2 ng/ml, so a level of 1.8 ng/ml would fall within the safe range, not pose a danger.

Correct Answer: D

Rationale: The correct answer is D because loratadine is a second-generation antihistamine that works by blocking the effects of histamine on peripheral tissues. This helps to alleviate symptoms of allergies such as pruritus and skin wheals. Option A is incorrect because loratadine does not block the release of histamine from mast cells. Option B is incorrect as loratadine does not prevent the antigen-antibody reaction. Option C is incorrect because loratadine does not elicit effects opposite to histamine; instead, it counteracts histamine effects.

Correct Answer: B

Rationale: The correct answer is B: Trigeminal nerve. Sumatriptan is a serotonin receptor agonist that acts on serotonin receptors in the trigeminal nerve to reduce inflammation and pain associated with migraines. The trigeminal nerve is a key player in the pathophysiology of migraines, transmitting pain signals from blood vessels and meninges to the brain. The other choices (A: Nucleus accumbens, C: Vestibular nuclei, D: Chemoreceptor trigger zone) are not directly involved in the pathophysiology of migraines or the mechanism of action of sumatriptan. The nucleus accumbens is primarily associated with reward and motivation, the vestibular nuclei are involved in balance and spatial orientation, and the chemoreceptor trigger zone is related to the regulation of vomiting.

Correct Answer: D

Rationale: Most drugs are absorbed in the GI tract via passive diffusion (Choice D), driven by lipid solubility and concentration gradients across membranes. Active transport (Choice A) requires energy, filtration (Choice B) is minor for drugs, and endocytosis/exocytosis (Choice C) is rare for small molecules.

Correct Answer: B

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.